HR: 11:20h
AN: H42C-05    [Abstracts]
TI: A multi-isotope approach to characterize acid mine drainage in a hardrock alpine mine, Chaffe Co,Colorado.
AU: * Cordalis, D
EM: cordalis@colorado.edu
AF: University of Colorado, Geography Department, UCB 260, Boulder, CO 80309
AU: * Cordalis, D
EM: cordalis@colorado.edu
AF: Institute of Arctic and Alpine Research, 1560 30th St, Boulder, CO 80309
AU: Williams, M W
EM: markw@colorado.edu
AF: University of Colorado, Geography Department, UCB 260, Boulder, CO 80309
AU: Williams, M W
EM: markw@colorado.edu
AF: Institute of Arctic and Alpine Research, 1560 30th St, Boulder, CO 80309
AU: Wireman, M
EM: Wireman.Mike@epamail.epa.gov
AF: US EPA Region VIII, 999 18th Street, Suite 300, Denver, CO 80202
AU: Michel, R L
EM: rlmichel@usgs.gov
AF: USGS, 345 Middlefield RD MS 434, Menlo Park, CA 94025
AU: Manning, A
EM: amanning@usgs.gov
AF: USGS CR GD, Box 25046 , Denver, CO 80225
AB: Here we present information from an innovative suite of stable, radiogenic, and cosmogenic isotopes to better understand groundwater flowpaths and groundwater-surface water interactions in an applied acid mine drainage system. Stable water isotopes, tritium, helium-tritium, sulfur-35, and uranium 234/238 ratios were analyzed from precipitation, groundwater wells, interior mine drainages, and surface waters at the Mary Murphy Mine in Colorado to determine hydrologic transport mechanisms responsible for contaminated zinc releases. Hydrometric measurements suggested a snowmelt-driven pulse of elevated zinc in adit outflow. However, mixing models using stable water isotopes showed a regional groundwater signal in the adit outflow. Tritium values of 11 to 13 TU showed a slight enrichment of bomb spike water compared to snow values of about 9 TU, suggesting an older water source as well. Helium/tritium ratios on a subset of groundwater wells suggested that average residence times of alluvial wells ranged from 2.5 to 8 years. The combination of stable water isotopes and sulfur-35 (half-life of 87 days), showed that zinc-rich waters within the mine derived from infiltrating snowmelt more than a year old. However, measurement of sulfur-35 using low-level scintillation counts was compromised at times by the presence of uranium. We were able to remove the uranium through wet chemistry procedures, improving the accuracy of S-35 measurements. The U234/U238 ratio shows promise in discriminating between acid mine drainage and acid rock drainage. Acid rock drainage shows an unaltered ratio of 1:1, while acid mine drainage is enriched relative to the 1:1 equilibrium ratio. The combination of cosmogenic and stable isotopes within and near the Mary Murphy Mine may provide a useful tool for studying interactions between groundwater and surfacewater in a fractured rock setting. Remediation techniques can be directed more appropriately, and cost effectively, by the characterization of flowpaths within the mine as well.
DE: 1806 Chemistry of fresh water
DE: 1829 Groundwater hydrology
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting